This invention relates to rigid fiberglass ducts and more particularly relates to a method of making a rigid fiberglass duct having an integral bendable elbow.
Rigid fiberglass air ducts have been around for years and are constructed by wrapping uncured fiberglass around a mandrel to a specific thickness. The fiberglass wrapped mandrel is then surrounded by a cavity and baked at temperatures of approximately 400-500 degrees for a few minutes. This cures the resin-impregnated fiberglass forming a rigid tubular fiberglass air duct.
Generally, when a bend is encountered, an elbow is inserted between two ducts and secured by means of duct tape. However, this method is unsatisfactory as over a long period of use the duct tape can lose its adhesiveness and the duct separate from the elbow. This is a constantly recurring problem and the only solution presently available is to rewind the separated area of the fiberglass duct with duct tape. The separations usually occur because of the porosity of the rigid fiberglass duct, which allows the duct tape to dry out and peel off. It would be advantageous if an integral bendable elbow could be built into a section of fiberglass duct, thus, providing an effective solution to accommodating bends when installing the fiberglass ducts.